1. Field of the Invention
The present invention relates to a coordinate input device which can change a coordinate signal on the basis of a the amount of variation an electrostatic capacity of a conductor. A coordinate input device of this kind can move the position of a cursor shown on a display device such as a CRT, in the X-axis or Y-axis direction.
2. Description of the Prior Art
In a so-called mouse which is widely used as a coordinate input device, a ball housed in the mouse is rotated by manually pulling and/or pushing the mouse on a desk or a dedicated mat, the rotation of the ball is transmitted to a vane wheel, and the rotation of the vane wheel causes a photodiode (light receiving element) to be alternately switched between an ON-state and an OFF-state, thereby generating a pulse signal. A program in a microcomputer operates in accordance with the pulse signal so that the position of a cursor shown on a display device such as a CRT is moved in the X-axis or Y-axis direction. Also in a so-called track ball in which a ball is manually rotated, a mechanism similar to that of the above-mentioned mouse is employed.
In addition to the above-mentioned mouse and track ball, known coordinate input devices through which coordinates on a display device can be input include those wherein a so-called cross key or a so-called joy stick is operated.
However, a conventional mouse or track ball has mechanical portions such as a mechanism for converting the rotation of a ball into the rotation of a vane wheel. Such mechanical portions make the structure complicated, and tend to impose restrictions on the increase in the life period and on improvements in reliability. During the use of a mouse or track ball, moreover, an LED incorporated in the mouse or track ball always consumes power, and hence it is difficult to enhance power saving.
In a coordinate input device using a cross key or a joy stick, a coordinate signal is subjected to a vector conversion by conducting operations such as the pressing of the cross key or the tilting of the joy stick, so that a cursor moves on a display device. Therefore, the sense of operating the key hardly coincides the movement of the cursor, thereby producing a problem in that there easily arises incompatibility between the key operation and the cursor motion.
Under these conditions, recently, computer specialization, provision of multiple functions for a remote controller for home use, growth in sophistication of game software, and diversification of the location of the use of these apparatuses are developing. In view of these circumstances, there is a demand to develop a coordinate input device in which an increase in the life period and improvements in reliability can easily be realized, while the power consumption is small, and the movement of the cursor on a display device coincides with the sense of the manual operation so that no incompatibility between them arises.